A Schottky diode is an electronic component that can be used in high frequency, fast switching or other electronic circuits, for example, as a RF mixer or detector diode, a power rectifier, or a clamp diode. The Schottky diode can exploit a rectifying barrier at a metal-semiconductor interface (i.e., the mismatch in the energy position of the majority carrier band edge of a semiconductor and the metal Fermi level across a metal-semiconductor interface) for its operation. Conduction in the Schottky diode is controlled by thermionic emission of majority carriers over the barrier. The Schottky diode can thus be a majority carrier device with a switching speed which is not limited by minority carrier effects.
A Schottky diode may be fabricated as a discrete component or incorporated in an integrated semiconductor circuit. A typical Schottky diode structure can include a metal or metal silicide conductive layer in rectifying contact with a semiconducting layer. Even though the Schottky diode can have good forward switching characteristics, in a reverse biased Schottky diode, large electric fields at the edges of the contact layer or rectifying barrier can lead to relatively low breakdown voltages and/or relatively poor leakage characteristics. To address relatively large edge electric fields that may be present, in conventional Schottky diode structures, the edge of the Schottky contact layer is placed on a field relief guard ring (i.e. a diffused oppositely-doped semiconductor region). The guard ring, which is in ohmic contact with the metal or metal silicide conductive layer, can improve reverse breakdown characteristics of the Schottky diode. The guard ring, however, can introduce a parasitic bipolar junction transistor in the structure. The parasitic bipolar junction transistor in action or active state can amplify small emitter-base currents to produce relatively large substrate currents to degrade the forward characteristics of the Schottky diode.